From 17be5dc7969f21d99a40cb116f84067eee54923b Mon Sep 17 00:00:00 2001
From: Craig Tiller <ctiller@google.com>
Date: Wed, 1 Jul 2015 10:36:27 -0700
Subject: [PATCH] Fix a list management bug exposed by new locking scheme in
 client_channel

---
 src/core/transport/chttp2/internal.h     |  8 ++++++
 src/core/transport/chttp2/stream_lists.c | 18 +++++++++++++
 src/core/transport/chttp2_transport.c    | 34 +++++++++++++++---------
 3 files changed, 48 insertions(+), 12 deletions(-)

diff --git a/src/core/transport/chttp2/internal.h b/src/core/transport/chttp2/internal.h
index c8c46f0e544..7f98a5bd711 100644
--- a/src/core/transport/chttp2/internal.h
+++ b/src/core/transport/chttp2/internal.h
@@ -63,6 +63,7 @@ typedef enum {
   GRPC_CHTTP2_LIST_WRITABLE_WINDOW_UPDATE,
   GRPC_CHTTP2_LIST_PARSING_SEEN,
   GRPC_CHTTP2_LIST_CLOSED_WAITING_FOR_PARSING,
+  GRPC_CHTTP2_LIST_CANCELLED_WAITING_FOR_WRITING,
   GRPC_CHTTP2_LIST_INCOMING_WINDOW_UPDATED,
   /** streams that are waiting to start because there are too many concurrent
       streams on the connection */
@@ -526,6 +527,13 @@ int grpc_chttp2_list_pop_closed_waiting_for_parsing(
     grpc_chttp2_transport_global *transport_global,
     grpc_chttp2_stream_global **stream_global);
 
+void grpc_chttp2_list_add_cancelled_waiting_for_writing(
+    grpc_chttp2_transport_global *transport_global,
+    grpc_chttp2_stream_global *stream_global);
+int grpc_chttp2_list_pop_cancelled_waiting_for_writing(
+    grpc_chttp2_transport_global *transport_global,
+    grpc_chttp2_stream_global **stream_global);
+
 void grpc_chttp2_list_add_read_write_state_changed(
     grpc_chttp2_transport_global *transport_global,
     grpc_chttp2_stream_global *stream_global);
diff --git a/src/core/transport/chttp2/stream_lists.c b/src/core/transport/chttp2/stream_lists.c
index c6ba12fca87..f04e763387c 100644
--- a/src/core/transport/chttp2/stream_lists.c
+++ b/src/core/transport/chttp2/stream_lists.c
@@ -282,6 +282,24 @@ int grpc_chttp2_list_pop_closed_waiting_for_parsing(
   return r;
 }
 
+void grpc_chttp2_list_add_cancelled_waiting_for_writing(
+    grpc_chttp2_transport_global *transport_global,
+    grpc_chttp2_stream_global *stream_global) {
+  stream_list_add(TRANSPORT_FROM_GLOBAL(transport_global),
+                  STREAM_FROM_GLOBAL(stream_global),
+                  GRPC_CHTTP2_LIST_CANCELLED_WAITING_FOR_WRITING);
+}
+
+int grpc_chttp2_list_pop_cancelled_waiting_for_writing(
+    grpc_chttp2_transport_global *transport_global,
+    grpc_chttp2_stream_global **stream_global) {
+  grpc_chttp2_stream *stream;
+  int r = stream_list_pop(TRANSPORT_FROM_GLOBAL(transport_global), &stream,
+                          GRPC_CHTTP2_LIST_CANCELLED_WAITING_FOR_WRITING);
+  *stream_global = &stream->global;
+  return r;
+}
+
 void grpc_chttp2_list_add_incoming_window_updated(
     grpc_chttp2_transport_global *transport_global,
     grpc_chttp2_stream_global *stream_global) {
diff --git a/src/core/transport/chttp2_transport.c b/src/core/transport/chttp2_transport.c
index 4bcb317fe79..a7f9af5c0c4 100644
--- a/src/core/transport/chttp2_transport.c
+++ b/src/core/transport/chttp2_transport.c
@@ -765,21 +765,31 @@ static void unlock_check_read_write_state(grpc_chttp2_transport *t) {
     }
   }
 
+  if (!t->writing_active) {
+    while (grpc_chttp2_list_pop_cancelled_waiting_for_writing(transport_global, &stream_global)) {
+      grpc_chttp2_list_add_read_write_state_changed(transport_global, stream_global);
+    }
+  }
+
   while (grpc_chttp2_list_pop_read_write_state_changed(transport_global,
                                                        &stream_global)) {
     if (stream_global->cancelled) {
-      stream_global->write_state = GRPC_WRITE_STATE_SENT_CLOSE;
-      stream_global->read_closed = 1;
-      if (!stream_global->published_cancelled) {
-        char buffer[GPR_LTOA_MIN_BUFSIZE];
-        gpr_ltoa(stream_global->cancelled_status, buffer);
-        grpc_chttp2_incoming_metadata_buffer_add(
-            &stream_global->incoming_metadata,
-            grpc_mdelem_from_strings(t->metadata_context, "grpc-status",
-                                     buffer));
-        grpc_chttp2_incoming_metadata_buffer_place_metadata_batch_into(
-            &stream_global->incoming_metadata, &stream_global->incoming_sopb);
-        stream_global->published_cancelled = 1;
+      if (t->writing_active && stream_global->write_state != GRPC_WRITE_STATE_SENT_CLOSE) {
+        grpc_chttp2_list_add_cancelled_waiting_for_writing(transport_global, stream_global);
+      } else {
+        stream_global->write_state = GRPC_WRITE_STATE_SENT_CLOSE;
+        stream_global->read_closed = 1;
+        if (!stream_global->published_cancelled) {
+          char buffer[GPR_LTOA_MIN_BUFSIZE];
+          gpr_ltoa(stream_global->cancelled_status, buffer);
+          grpc_chttp2_incoming_metadata_buffer_add(
+              &stream_global->incoming_metadata,
+              grpc_mdelem_from_strings(t->metadata_context, "grpc-status",
+                                       buffer));
+          grpc_chttp2_incoming_metadata_buffer_place_metadata_batch_into(
+              &stream_global->incoming_metadata, &stream_global->incoming_sopb);
+          stream_global->published_cancelled = 1;
+        }
       }
     }
     if (stream_global->write_state == GRPC_WRITE_STATE_SENT_CLOSE &&